Alert archive / Illinois / Mesoscale Discussions in 2012
Mesoscale Discussion 1497
The Storm Prediction Center issued this mesoscale discussion at Jul 18, 2012, 6:56 PM CDT for 4 states. It was in force for 94 min.
The area
The outline as issued.
The facts
- Issued
- Jul 18, 2012, 6:56 PM CDT (23:56 UTC)
- Expired
- Jul 18, 2012, 8:30 PM CDT
- In force
- 94 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 493
All 31 counties
Boone County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, McHenry County, IL, Ogle County, IL, Stephenson County, IL, Will County, IL, Winnebago County, IL, Lake County, IN, LaPorte County, IN, Porter County, IN, Starke County, IN, Berrien County, MI, Columbia County, WI, Dane County, WI, Green County, WI, Iowa County, WI, Jefferson County, WI, Kenosha County, WI, Lafayette County, WI, Racine County, WI, Rock County, WI, Sauk County, WI, Walworth County, WI, Waukesha County, WI
The radar
The Milwaukee radar (KMKX), 51 km from the middle of the area, began a volume at 23:56 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Davenport, (KDVN), launched 12:00Z, 11.9 hours before the alert went out and 174 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 1900 J/kg
- Mixed-layer CIN
- -67 J/kg
- Mixed-layer LCL
- 1674 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 35 m²/s²
- 0-3 km storm-relative helicity
- 44 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
061
ACUS11 KWNS 182356
SWOMCD
SPC MCD 182356
INZ000-MIZ000-ILZ000-WIZ000-190130-
MESOSCALE DISCUSSION 1497
NWS STORM PREDICTION CENTER NORMAN OK
0656 PM CDT WED JUL 18 2012
AREAS AFFECTED...SRN WI...NRN IL...NW IND AND SRN LAKE MI
CONCERNING...SEVERE THUNDERSTORM WATCH 493...
VALID 182356Z - 190130Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 493
CONTINUES.
SUMMARY...A SEVERE THREAT WILL LIKELY CONTINUE FOR A FEW MORE HOURS
ACROSS SE WI...NE IL AND MAY DEVELOP ACROSS SRN LAKE MI AND NW IND.
WIND DAMAGE AND HAIL WILL LIKELY BE THE PRIMARY THREATS. THE WATCH
MAY NEED A LOCAL EXTENSION IN TIME IN THE CHICAGO AND MILWAUKEE
AREAS BEYOND THE 01Z EXPIRATION OR A SMALL NEW WATCH WILL LIKELY
NEED TO BE ISSUED.
DISCUSSION...A BOWING LINE SEGMENT IN SRN WI IS CURRENTLY LOCATED
ALONG A NARROW AXIS OF MODERATE INSTABILITY WHERE MESOANALYSIS SHOWS
MLCAPE VALUES AROUND 1500 J/KG IN SRN WI. THE MODERATE INSTABILITY
EXTENDS SEWD ACROSS NE IL INTO NW IND. THE EXPECTED TRACK OF THE
LINE SEGMENT IS EXPECTED TO BE ON THE NRN EDGE OF MODERATE
INSTABILITY WITH THE LINE MOVING ESEWD ACROSS SRN LAKE MI. IF THIS
HAPPENS...THE LINE SEGMENT COULD WEAKEN AS IT ENCOUNTERS THE MORE
STABLE AIRMASS OVER THE LAKE. IF THE LINE CAN TURN MORE TO THE
RIGHT...THEN A CONTINUING SEVERE THREAT THIS EVENING WOULD BE MORE
PROBABLE WITH A WW EXTENSION LIKELY NEEDED ACROSS PARTS OF NE IL AND
NW IND.
..BROYLES/THOMPSON.. 07/18/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...IWX...LOT...MKX...DVN...ARX...
LAT...LON 42048628 43238851 43638959 43619004 43419027 43099040
42589042 42209008 41228835 41028671 42048628SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 18, 11:38 AM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, DeKalb, DuPage, Grundy and 11 more | 67 min |
| Jul 18, 12:58 PM CDT | Severe Thunderstorm Watch | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 22 more | 7 hr |
| Jul 18, 3:07 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, DeKalb, DuPage, Grundy and 20 more | 53 min |
| Jul 18, 11:54 AM CDT | Mesoscale Discussion | SPC | Adams, Allen, Blackford, Decatur, Delaware, Fayette and 15 more | 2 hr |
| Jul 18, 12:16 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Allen, Bartholomew, Blackford, Carroll, Cass and 28 more | 8 hr |
| Jul 18, 3:21 PM CDT | Mesoscale Discussion | SPC | Bartholomew, Blackford, Boone, Brown, Cass, Clinton and 30 more | 84 min |
Nearby
Mesoscale Discussions in Illinois, 2012Mesoscale Discussions in Wisconsin, 2012Mesoscale Discussions in Indiana, 2012Every mesoscale discussion in 2012
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.